Generally, bump and texture mapping are processes where basic contours of an object are expressed as a polygon in a modeling process and real world map data is used for a rendering process. During the course of bump and texture mapping, a color calculation is performed to incorporate colors onto an object in display coordinate space. This object with the colors is then displayed on a display device.
Prior Art FIG. 1 illustrates the method by which an exemplary bump mapping process is accomplished. As shown, a primitive, i.e. polygon, triangle, etc., is first received with pixel data, as shown in operation 100. Included with such pixel data are normal values and possibly other values associated with the vertices associated with the polygon. These vectors are perspectively and correctly interpolated across the primitive. At each pixel, texture coordinates (also interpolated) are used to look up bump mapping information.
During bump mapping, the aforementioned normal values are modified based on a bump map algorithm using the bump mapping information, as indicated in operation 102 of FIG. 1. In particular, the normal's direction is perturbed as though the surface has been displaced a small amount in the direction of the interpolated normals of the primitive. FIG. 2 illustrates a primitive 200 with a normal 202 that is modified to generate a perturbed normal 204. A bumpy surface is thereby simulated.
Thereafter, lighting operations such as shading or the like are performed on the pixel data using the perturbed normal values instead of the original normal values, as indicated in operation 104. This method gives the appearance of bumps and depressions in the surface. Also at this time, the color calculation may be carried out in order to enhance the color of the pixel.
While the foregoing bump and texture mapping techniques feature the unevenness of a surface and enhance the color of a pixel, they do not work well to reflect any unevenness in shadows cast by or onto the bumpy surface. Further, there are also limitations as to the interaction of geometric objects. These drawbacks are mainly due to the fact that conventional bump and texture mapping processes have no impact on the z-value of the pixel.
There is thus a need for a texture/bump mapping scheme during graphic processing that overcomes these drawbacks for providing a more realistic rendered image.